Resin film forming method, and laminate production method and apparatus

ABSTRACT

In the resin film forming method for extruding a fused resin from an extruder die to form a resin film, the second resin forming both ends in width direction of the resin film uses a resin greater in extension viscosity than the first resin forming the center in width direction of the resin film. Thereby, even if production conditions such as resin condition and operating conditions change, faults such as neck-in and its resultant thickening at both ends of the resin film can be suppressed. In the production of a laminate by nipping a support and a resin film of a thermoplastic resin by means of a nip roller and a cooling roller while coating the resin film onto the surface of the support, the accompanying air following the rotation of the cooling roller to the nip point is shut off by blowing a gas permeable through the resin film from a gas jet nozzle toward the surface of the cooling roller. Thereby, the occurrence of craters can be inhibited, a laminate excellent in surface appearance can be produced and the production of a laminate effective especially at the time of a line speed rise in the laminate production is performable.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a resin film forming method, toa laminate production method and apparatus and in particular to an artof suppressing a neck-in phenomenon or the like in extruding a resinfrom an extruder die to form a resin film and inhibiting the occurrenceof craters on a resin film surface of a laminate.

[0003] 2. Description of the Related Art

[0004] Generally on extruding a resin from a extruder die to form aresin film and producing a film-shaped product from this resin film or afilm-shaped stack obtained by laminating or coating the resin film ontoa support, a phenomenon known as so-called neck-in occurs, in which theextruded film has a width smaller than the extruding width. It isaccompanied with a problem that the film thickness at both ends in widthdirection of the resin film becomes greater than that at the center.Furthermore, in case of forming a resin film at high speed owing to thespeedup of production line, there is also a problem that a phenomenon offilm shake takes place owing to the unstable both ends in widthdirection of the resin film and the film width is not kept constant,thereby decreasing the yield. In this case, a technique of resin edgestacking in width direction is present principally for purposes ofrecycling-up, but there is a problem that a film is separated betweenthe central resin and the marginal resin of the resin film at the timeof edge stacking of resins different in physical property.

[0005] Namely, in forming of a resin film by using an extruder die,there are principally (1) a problem of neck-in and its accompanyingincrease in thickness at both resin ends, (2) a problem of film shakeand (3) a problem of film separation originating from the difference ofresin in physical property between the center and both ends of a resinfilm and thus measures to improve these have been desired. Theseproblems are not limited to the case of extruding a resin from anextruder die but take place also in case of ejecting a coat liquid froman extruder die.

[0006] So far, as countermeasures against the above problems, there havebeen adopted a method for improving the material physical property bymixing a plurality of materials (Japanese Patent Publication Nos.64-3655 and 5-82806), a method of changing the flow of a resin in theextruder die (Japanese Patent Publication Nos. 6-61819 and 64-64822) anda method of cooling both ends of the resin film extruded from anextruder die (Japanese Patent Publication No. 5-33134).

[0007] However, the method for improving the material physical propertyhas a drawback of deficiency in general usability because a suitableadditive must be added for each material. The method of changing theflow of a resin in the extruder die by using a forming plate has adrawback of being ineffective for the film shake though effective forthe suppression of neck-in. The method of cooling both ends of the resinfilm extruded from an extruder die has a drawback that no stable effectcan be obtained in case of an increase in line speed.

[0008] Widely adopted in the production of a laminate such as supportfor photo printing paper is an extrusion laminate method (also referredto as an extrusion coating method) of laminating a resin film on asupport by not only coating but also nipping a resin film of athermoplastic resin such as polyolefin extruded from an extruder die toa running support for pressure adhesion at the nip point between a niproller and a cooling roller.

[0009] In the production of this laminate, minute pores (hereinafter,referred to as craters) may appear on the surface of the resin filmlaminated on a support. When the number of these craters is great, theouter appearance of a product is damaged, and the glossy feeling alsolowers in the case of the laminate being used as a photoprint papersupport, for example, so that the product markedly decreases in value.The occurrence of craters is attributable to the fact that theaccompanying air is, under influence of the accompanying air generatedon the rotation of a cooling roller, accumulated in the area between theresin film and the cooling roller and a convex recess arises on theresin film. With increasing line speed in the production of a laminate,with decreasing thickness of the resin film, with lowering dischargetemperature of a resin from the extruder die, with smaller nip pressureand with greater surface roughness of a support, craters become morelikely to occur.

[0010] As preventive measures against the occurrence of craters, variousexaminations have been made, for example, from the viewpoint of a resinlike Japanese Patent Application Publication No. 8-36238, from theviewpoint of an improvement in the surface of a support like JapanesePatent Application Publication No. 4-81836, on the basis of specifyingthe process conditions like Japanese Patent Application Publication No.6-214342 and on the basis of proposing a new equipment for spraying agas permeable through a resin film toward the nip point like JapanesePatent Application Publication No. 63-246227.

[0011] Though effective in its own way, however, the above-mentionedpreventive measures against the occurrence of craters involved a problemthat no sufficient effect could be obtained in case of a line speed risein the production of a laminate.

[0012] In this case, the provision of a windshield plate has beenproposed as a further improvement of the equipment in Japanese PatentApplication Publication No. 63-246227, but is not fully effective incase of speedup to a high speed range equal to or greater than 300 m/minand a contact of the windshield plate with a cooling roller brings abouta fear of damaging the cooling roller.

SUMMARY OF THE INVENTION

[0013] The present invention has been developed in view of theabove-described circumstances, and has as its object the provision of amethod for forming a resin film capable of suppressing the neck-in andits accompanying thickening of a resin film at both ends and suppressingthe film shake entailing the fluctuation of width in the resin film evenwhen production conditions such as resin condition and operatingcondition change, and further preventing the film separation even inpresence of a difference in the physical property between both ends andthe center of the resin film.

[0014] A further object of the present invention is to provide alaminate production method and apparatus, capable of inhibiting theoccurrence of craters to produce a laminate excellent in surfaceappearance, and in particular effective in case of a line speed rise inthe production of a laminate.

[0015] In order to achieve the above-described objects, the presentinvention is directed to a resin film forming method for extruding fusedresin from an extruder die to form a resin film, wherein a resin formingboth ends in width direction of the resin film has an extensionviscosity higher than that of a resin forming a center in widthdirection of the resin film.

[0016] Thereby, the neck-in and its accompanying film thickening of bothends of the resin film can be suppressed. The film shake that the widthof the resin film fluctuates in accompaniment with the suppressingeffect of the neck-in can be also suppressed.

[0017] In order to achieve the above-described objects, the presentinvention is also directed to a resin film forming method for extrudingfused resin from an extruder die to form a resin film, wherein a resinforming both ends in width direction of the resin film has an MFRsmaller than that of a resin forming a center in width direction of theresin film.

[0018] Thereby, the neck-in and its accompanying film thickening of bothends of the resin film can be suppressed. The film shake that the widthof the resin film fluctuates in accompaniment with the suppressingeffect of the neck-in can be also suppressed.

[0019] In order to achieve the above-described objects, the presentinvention is also directed to a resin film forming method for extrudingfused resin from an extruder die to form a resin film, wherein a resinforming both ends in width direction of the resin film has a higherextension viscosity and smaller MFR than those of a resin forming acenter in width of the resin film.

[0020] Thereby, the neck-in and the film shake can be suppressed stillmore.

[0021] The MFR means the number of grams representing the amount of anextruded thermoplastic resin from an orifice, 2.1 mm in diameter and 8mm in length, for 10 min when subjected to a force of 2310 g (44 pis) at230° C. (refer to JIS K 7210, ASTMD 1238 for the measuring method). Ingeneral, with greater resin in MFR, the fluidity and machinability in amolten state become better, but the extension strength and the likedecreases.

[0022] Preferably, the resin forming both ends of the resin film joinsthe resin forming the center of the resin film so as to be enveloped bythe later resin and is extruded from the extruder die.

[0023] Thereby, the neck-in and the film shake cannot only be suppressedstill more but the film separation can also be prevented from occurrenceeven if both ends and the center of the resin film differ in physicalproperty to certain extent.

[0024] In order to achieve the above-described objects, the presentinvention is also directed to a laminate production method for producinga laminate by nipping a running support and a resin film ofthermoplastic resin by means of a nip roller and a cooling roller whilecoating the surface of the support with the resin film, wherein theaccompanying air brought with rotation of the cooling roller to a nippoint for the support and the resin film is shut off by blowing a gaspermeable through the resin film toward the surface of the coolingroller.

[0025] In order to achieve the above-described objects, the presentinvention is also directed to a laminate production apparatus forproducing a laminate by nipping a running support and a resin film ofthermoplastic resin by means of a nip roller and a cooling roller whilecoating the surface of the support with the resin film, wherein a gasjet nozzle for jetting a gas permeable through the resin film toward thesurface of the cooling roller is provided near a nip point for thesupport and the resin film.

[0026] According to the present invention, gas permeable through theresin film is blown from the gas jet nozzle toward the cooling rollersurface to form a gas curtain so that the accompanying air flowingtoward the nip point in accompaniment with the rotation of the coolingroller is shut off. Thereby, the occurrence of craters can be inhibitedand a laminate excellent in surface outer appearance can be produced. Inparticular, even for a rise in the line speed of laminate production,the occurrence of craters can be effectively inhibited and furthercraters can be noticeably decreased, thus enabling the film thickness ofthe resin film to be also reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The nature of this invention, as well as other objects andadvantages thereof, will be explained in the following with reference tothe accompanying drawings, in which like reference characters designatethe same or similar parts throughout the figures and wherein:

[0028]FIG. 1 is a configurational drawing of a film-shaped stackproduction apparatus to which a resin film forming method according tothe present invention;

[0029] FIGS. 2(a) and 2(b) are illustrations of an extruder die,represented in a top view and a side view, respectively;

[0030] FIGS. 3(a) and 3(b) are typical views of an section in widthdirection of the resin film extruded from an extruder die;

[0031]FIG. 4 is an overall configurational drawing of a laminateproduction apparatus according to the present invention;

[0032]FIG. 5 is a table explaining the examples of resin film formingmethods according to the present invention; and

[0033]FIG. 6 is a table explaining the examples of laminate productionmethods according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0034] Hereunder preferred embodiments will be described in details fora resin film forming method according to the present invention inaccordance with the accompanying drawings.

[0035]FIG. 1 shows a general configurational drawing showing one exampleof production apparatus to which a resin film forming method accordingto the present invention is applied and the present invention will bedescribed referring to one example of apparatus for producing afilm-shaped stack with a resin film laminated to a support.

[0036] As shown in FIG. 1, a cooling roller 14 and a nip roller 16 aredisposed adjacently in parallel below an extruder die 12 for extruding afused resin to form a resin film 11 and moreover a peeling roller 18 isdisposed adjacently in parallel with the cooling roller 14 opposite thenip roller 16 with the cooling roller 14 placed therebetween. Afterstuck to a belt-shaped support 22 conveyed from the upstream, the resinfilm 11 extruded from the extruder die 12 passes between the coolingroller 14 and the nip roller 16 and between the cooling roller 14 andthe peeling roller 18, runs in contact with the periphery of the coolingroller 14 and departs from the cooling roller 14 at the position of thepeeling roller 18. Thereby, a film-shaped stack 27 is produced. As thesupport 22, paper, polyethylene or a metal can be used depending on arequired film-shaped stack 27. As resins forming a resin film,publicly-known thermoplastic resins including polyolefin resin such aspolyethylene or polypropylene can be used.

[0037] FIGS. 2(a) and 2(b) are schemas of an extruder die 12,represented in a front view and a side view, respectively.

[0038] As shown in FIGS. 2(a) and 2(b), the extruder die 12 chieflycomprises a manifold 28 for spreading the resin supplied into theextruder die 12 in the width direction of the extruder die 12 (in widthdirection of a resin film), a slit 30 for extruding a resin outward fromthe manifold 28 as a resin film 11, a trunk flow path 32 in which afirst resin 11A forming the center in width direction of the resin filmand branch flow paths 34 and 34 in which a second resin 11B forming bothends in width direction of the resin film. The first resin 11A joins thesecond resin 11B, both of which are extruded from slit discharge port30A in a joined state of two resins. The first resin 11A and the secondresin 11B may join together in the extruder die 12 as shown here or mayjoin together before supplied to the extruder die 12. Thereby, thejoined resin is extruded in the form of resin film 11 from the extruderdie 12, and the resin film is formed of the first resin 11A at thecenter and formed of the second resin 11B at both ends. In this case, itis preferable as the second resin 11B to use a resin greater inextension viscosity than the first resin 11A. It is preferable as thesecond resin 11B to use a resin smaller in MFR than the first resin 11A.The first resin 11A is allowable to form one layer by using a singleresin or to form multiple layers by using a plurality of resins and tocontain an organic pigment, an additive or the like. The second resin11B is allowable to be made of at least one kind or more of resins andto contain an additive or the like, but is preferably made of a singleresin if a trimming loss (a loss due to a cutting the ear portionforming both ends of a product at the subsequent step) is considered.

[0039] FIGS. 3(a) and 3(b) are schematic representations of a section inwidth direction of the resin film 11 extruded from an extruder die 12and show a relation between a first resin 11A forming the center inwidth direction of the resin film and a second resin 11B forming bothends in width direction of the resin film.

[0040]FIG. 3(a) corresponds to the case where both resins are arrangedso that the second resin 11B is adjacent to both ends in width directionof the first resin 11A, whereas FIG. 3(b) corresponds to the case whereboth resins are arranged so that the second resin 11B is enveloped inthe first resin 11A. In comparison between FIG. 3(a) and FIG. 3(b), theresultant film-shaped stack can be prevented from separating from eachother as a single film by arranging the second resin 11B so as to beenveloped in the first resin 11A as shown in FIG. 3(b), even if theydiffer in physical property to a certain extent.

[0041]FIG. 3(b) represents one example of the second resin 11B envelopedin the first resin 11A so that the second resin 11B forms two islandsfor each end in width direction of the first resin 11A, where one islandmay be arranged so as to be formed or two or more islands may bearranged so as to be formed. In order to form two islands or more, it isonly necessary to make the number of branch flow paths 34 correspondentto the number of islands to which the second resin 11B is supplied.

[0042] Next, using a film-shaped stack production apparatus 10constructed as mentioned above, a production method according to thepresent invention will be described.

[0043] The first resin 11A and the second resin 11B supplied to theextruder die 12 joins together in a state above the melting points ofindividual resins so that both resins unites with each other, the centeris formed of the first resin 11A and at the same time both ends areextruded from a slit discharge port 30A as the resin film 11 formed ofthe second resin 11B. After oxidized with an oxidized gas such as air orozone so that a sufficient adhesion with the support 22 conveyed fromthe upstream is obtained, the resin film 11 extruded from the extruderdie 12 is nipped between the cooling roller 14 and the nip roller 16 andthus laminated to the support 22. Then, after cooled sufficiently byusing the cooling roller 14, the resin film 11 is peeled from thecooling roller 14 by using a peeling roller 18. Thereby, a film-shapedstack 27 with a resin film 11 laminated to the support 22 is produced.

[0044] Since a resin greater in extension viscosity than the first resin11A forming the center in width direction of the resin film is soarranged as to be used for the second resin 11B forming both ends inwidth direction of the resin film in forming the resin film 11 by usingthe extruder die 12 when this film-shaped stack 27 is produced, theneck-in can be reduced. The greater the preventive effect of neck-in is,the more effectively the film shake that the width of the resin film 11fluctuates can be prevented. In this case, it is preferable that theratio of the second resin 11B to the first resin 11A in extensionviscosity (hereinafter, referred to as “extension viscosity ratio”) isnot greater than 10 at the upper limit. This is because the differencein physical property between the first resin 11A and the second resin11B became too great if the extension viscosity ratio exceeds 10 times,which likely to mainly cause the film separation.

[0045] Causes for the neck-in are considered variously, but, in the caseof producing a film-shaped stack, are attributable to a contraction inthe resin film 11 caused by the presence of speed distribution in thewidth direction of the resin film 11, which is generated when the speedchanges from the speed of winding at the cooling roller 14 to the speedof extruding from the extruder die 12. On the other hand, the degree ofcontraction differs depending on the viscosity of a resin. As forviscosity, there are shear viscosity and extension viscosity andordinarily, when viscosity is simply referred to as, it points to shearviscosity, but the inventers have found that the extension viscosity hasa closer relation with the degree of contraction. Thus, it is found thatthe neck-in can be suppressed in bounds and leaps by disposing a secondresin 11B at both ends of the resin film 11 that is greater in extensionviscosity than the first rein 11A forming the center in width directionof the resin film 11 and unlikely to generate the neck-in. In this case,since the extension viscosity does not necessarily increase even if theshear viscosity is raised, it is important to suppress the neck-in bymanaging the extension viscosity.

[0046] By using a resin smaller in MFR than the first resin 11A as thesecond resin 11B, the neck-in can be effectively suppressed. The greaterthe suppression effect against the neck-in is, the more effectively thefilm shake of fluctuations in the width of a resin film 11 can beprevented. In this case, it is preferable that the ratio of the secondresin 11B to the first resin 11A in MFR (hereinafter, referred to as“MFR ratio”) is not smaller than 1/10 at the lower limit. This isbecause the difference in physical property between the first resin 11Aand the second resin 11B became too great if the MFR ratio is less than1/10, which likely to mainly cause the film separation.

[0047] Furthermore, by joining the second resin 11B with the first resin11A so as to be enveloped therein, the resultant film can be preventedfrom mutual separation even if the first resin 11A and the second resin11B differ in physical property to a certain extent. In this case, sincethe contact area of the second resin 11B with the first resin 11A can beincreased if dividing the second resin 11B into multiple parts as shownin FIG. 3(b), the film separation can be prevented effectively even incase of high speed formation of a resin film 11 or even when the secondresin 11B is greater in physical property than the first resin 11A to acertain extent. If the number of dividing the second resin 11B is toogreat, however, the flow rate worsens in uniformity and the branch flowpaths 34 becomes difficult in machinability and therefore it isadvisable to set the number of divisions appropriately withconsideration of a trade-off between the properties of the first resin11A and the second resin 11B.

[0048] When a film-shaped stack with a resin film laminated onto asupport 22 is produced like this embodiment, the cooling roller 14 isnot sufficiently cooled and a trouble of no peeling from the coolingroller 14 is apt to occur for a thick film at both ends of the resinfilm, but with the present embodiment, the temperature down only at bothends of the resin film is performable and the film thickness can bedecreased, so that such a trouble can be prevented.

[0049] In the present embodiment, the descriptions have been made usingan example of producing a film-shaped stack with a resin film 11laminated onto a support 22, but the present invention is alsoapplicable to a film production process for producing a film-shapedproduct and to a coat process for ejecting a coat liquid in the shape ofa film to coat it to a support.

[0050] Next, preferable embodiments of laminate production method andapparatus according to the present invention will be described indetails.

[0051]FIG. 4 is a general configurational drawing of a laminateproduction apparatus 110 according to an embodiment of the presentinvention.

[0052] As shown in FIG. 4, a cooling roller 116 and a nip roller 118 aredisposed adjacently in parallel below an extruder die 114 for extrudinga resin film 112 of a fused thermoplastic resin and at the same time apeeling roller 120 is disposed adjacently in parallel with the coolingroller 116 opposite the nip roller 118 with the cooling roller 116placed therebetween. Furthermore, opposite the cooling roller 116 withthe nip roller 118 placed therebetween, a backup roller 122 is provided.A running belt-shaped support 124 is nipped at the nip point P where thecooling roller 116 and the nip roller 118 make contact with each otherwhile the resin film 112 extruded from the extruder die 114 is coated.The support 124 coated with the resin film 112 runs while the resin filmsurface is brought into contact with the surface of the cooling roller116, thus is cooled and is peeled from the cooling roller 116 by meansof the peeling roller 120. Thereby, a laminate 127 is produced.

[0053] Near the nip point P between the support 124 and the resin film112, a gas jet nozzle 126 for jetting a gas toward the surface of thecooling roller 116 is provided. As gases to be jetted from the gas jetnozzle 126, gases permeable through the resin film 112 such as e.g., CO₂gas, O₂ gas, H₂O gas and He gas can be used. The gas jet nozzle 126 isformed in the shape of a throttle long in width direction of the coolingroller 116 and thereby the jetted gas forms a gas curtain extending fromthe nozzle tip to the cooling roller surface.

[0054] According to a laminate production apparatus 110 constructed asmentioned above, a gas permeable through the resin film 112 is sprayedto the surface of the cooling roller 116 from the gas jet nozzle 126 toform a gas curtain so that the accompanying air flowing toward the nippoint P in accompaniment with the rotation of the cooling roller 116 isshut off therefrom and converted into a permeable gas. Thereby, in anarea 128 surrounded by the resin film 112 and the cooling roller 116,the occurrence of craters can be effectively inhibited because even theaccompanying gas to the surface of the resin film 112 becomes difficultin forming a recess on the resin film 112 if permeable. Furthermore,since the accompanying air is shut off by a gas curtain, the cooling isnot damaged unlike the case of using a conventional windshield plate.

[0055] Like this, the present embodiment can inhibit the occurrence ofcraters and enables a laminate 127 excellent in surface appearance to beproduced. In particular, even in the high speed region of line speed asexceeding 300 m/min, the occurrence of craters can be effectivelyinhibited, thereby enabling the productivity to be raised. Furthermore,since the number of craters can be noticeably decreased, the filmthickness of the resin film 112 can be also lowered, thereby enablingthe cost of raw materials to be saved. Since the vicinity of theextruder die 114 is also turned into a gas atmosphere according to thepresent embodiment, the occurrence of a die stripe can be inhibited.

[0056] With reference to FIG. 4, a position in the vicinity of the nippoint P for installing the gas jet nozzle 126 is preferably determinedso that the central angle α between the line connecting the center O ofthe cooling roller 116 with the nip point P and the line connecting thecenter O with a blown point Q on the surface of the cooling roller 116for blow from the gas jet nozzle 126, which angle represents the arcdistance on the cooling roller 116 from the blown point Q to the nippoint P (hereinafter, referred to as “distance from the nip point”), is90 degrees or less, and more preferably 80 degrees or less. If the arcdistance from the nip point P to the blown point Q of central angle morethan 90 degrees, the blown gas diffuses and stable a gas curtain is notformed and therefore the effect decreases. The central angle for arcdistance from the nip point P is still better preferably 80 degrees orsmaller because the distribution is likely to occur with some gasexhaust methods or the like if exceeding 80 degrees. The blown angle βof a gas to the surface of the cooling roller 116 is within ±20° andpreferably within ±10° from the central direction of the cooling roller116 or from the direction vertical to the surface of the cooling roller116. The distance L from the tip of the gas jet nozzle 126 to thesurface of the cooling roller 116 (hereinafter, referred to as “distancefrom the cooling roller”) is 50 mm or smaller and preferably 40 mm orsmaller as the blow distance vertical to the surface of the coolingroller 116. If the distance from the cooling roller 116 exceeds 50 mm,the blown gas diffuses and stable a gas curtain is not formed andtherefore the effect decreases. Furthermore, the flow velocity of thegas blown from the gas jet nozzle 126 is preferably 1 m/sec or higherand well preferably 2 n/sec. If the gas flow velocity is lower than 1m/sec, the blown gas diffuses and stable a gas curtain is not formed andtherefore the effect decreases.

[0057] These conditions of the gas jet nozzle 126 are especiallyeffective when the line speed in producing a laminate 127 is raised to300 m/min or higher and the rotation of the cooling roller 116 isspeeded up. This is because in a manufacturing line with a very fastline speed of 300 m/min or more, the influence by the accompanying airof the cooling roller 116 increases, the shut off effect of theaccompanying air is hardly obtained to a sufficient extent only byblowing a gas to the surface of the cooling roller 116 and the gasreplaced once from air in the area surrounded by the resin film 112 andthe cooling roller 116 diffuses completely by the turbulent diffuse.

[0058] Meanwhile, the present embodiment is effective also when acooling roller with ruggedness on the surface is used to transfer thisruggedness to a laminate. Namely, if ruggedness is present on thesurface of the cooling roller 116, the accompanying air remains in arecess; but nevertheless, by carrying out the present embodiment, theair in this recess is replaced with a permeable gas and the replaced gaspermeates through the resin film, so that the ruggedness on the coolingroller surface is transferred more clearly to the resin film. Thus, evenif the resin film surface is a glossy surface, a matted surface, a silkysurface or the like, the quality of various surface species can beimproved.

EXAMPLES

[0059] Next, specific examples of resin film forming methods accordingto the present invention will be described referring to FIG. 5. Resinssubjected to tests were as follows. Two line speeds of 200 m/sec and 420m/sec were used for the execution of tests.

[0060] In First Comparative Example, a mixture of fused low densitypolyethylene, 10 g/10 min in MFR, 1.0 in nondimensional extensionviscosity and 0.917 g/cm³ in density with 10 wt % of titanium oxide wasextruded singly from the extruder die. In other words, the first resinalone was used and no second resin was used for the execution. Theextension viscosity was measured using a rheometer and was indicatednondimensionally in this example, setting 1000 p.a.s to therepresentative viscosity at the time of extension viscosity of 10(1/sec).

[0061] In Second Comparative Example, as the second resin forming bothends in width direction of a resin film, a 20 g/10 min MRF (MRF ratio:2) resin whose extension viscosity was a third of that of the firstresin forming the center in width direction of the resin film (extensionviscosity ratio 1/3) was used. As one whose center was formed of thefirst resin and both of whose ends were of the second resin, a resinfilm was extruded from the slit discharge port of the extruder die.Namely, the second resin in Second Comparative Example was greater inMFR and smaller in extension viscosity than the first resin, whichsignified a case not satisfying the present invention. The sectionalshape of a resin film when the first and second resins joined togetherwas arranged so that the second resin was enveloped in the first asshown in FIG. 3(b).

[0062] In First Example, as the second resin forming both ends in widthdirection of the resin film, a 8 g/10 min MFR (MFR ratio: 2) resin whoseextension viscosity was 1.2 times that of the first resin forming thecenter in width direction of the resin film (extension viscosity ratio1.2) was used. As one whose center was formed of the first resin andboth of whose ends were of the second resin, a resin film was extrudedfrom the slit discharge port of the extruder die. Namely, the secondresin in First Example was smaller in MFR and greater in extensionviscosity than the first resin, which signified a case satisfying thepresent invention. The sectional shape of the resin film was the samewith Second Comparative Example.

[0063] In Second Example, as the second resin forming both ends in widthdirection of the resin film, a 12 g/10 min MFR (MFR ratio: 1.2) resinwhose extension viscosity was 1.2 times that of the first resin formingthe center in width direction of the resin film (extension viscosityratio 1.2) was used. As one whose center was formed of the first resinand both of whose ends were of the second resin, a resin film wasextruded from the slit discharge port of the extruder die. Namely, thesecond resin in Second Example did not satisfy the present invention inMFR, but satisfied the present invention in extension viscosity. Thesectional shape of the resin film was the same with Second ComparativeExample.

[0064] In Third Example, as the second resin forming both ends in widthdirection of the resin film, a 8 g/10 min MFR (MFR ratio: 4/5) resinwhose extension viscosity was 0.9 times that of the first resin formingthe center in width direction of the resin film (extension viscosityratio 0.9) was used. As one whose center was formed of the first resinand both of whose ends were of the second resin, a resin film wasextruded from the slit discharge port of the extruder die. Namely, thesecond resin in Third Example satisfied the present invention in MFR,but did not satisfy the present invention in extension viscosity. Thesectional shape of the resin film was the same with Second ComparativeExample.

[0065] In Fourth Example, as the second resin forming both ends in widthdirection of the resin film, a 1.0 g/10 min MFR (MFR ratio: 1/10) resinwhose extension viscosity was 10 times that of the first resin formingthe center in width direction of the resin film (extension viscosityratio 10) was used. As one whose center was formed of the first resinand both of whose ends were of the second resin, a resin film wasextruded from the slit discharge port of the extruder die. Namely, thesecond resin in Fourth Example was noticeably smaller in MFR andnoticeably greater in extension viscosity than the first resin, whichsignified a case satisfying the present invention. The sectional shapeof the resin film was the same with Second Comparative Example.

[0066] In Third Comparative Example, the sectional shape of a resin filmwhen the first and second resins joined together was arranged so as toadjoin each other as shown in FIG. 3(a) and the other points were thesame with Fourth Example.

[0067] Regarding First to Fourth Examples and First to Third ComparativeExamples, the neck-in amount at one side of a resin film (L in FIG.2(a)) and the presence of film separation between the center and bothends of a resin film were compared.

[0068] As understood from the comparison between First and SecondComparative Examples and First to Fourth Examples in FIG. 5, the neck-inamount could be decreased if either MFR or extension viscosity satisfiedthe present invention, i.e. by setting the MFR ratio below 1 or theextension viscosity above 1.

[0069] When MFR did not satisfy the present invention and extensionviscosity satisfied the present invention in the second resin likeSecond Example or when MFR satisfied the present invention and extensionviscosity did not satisfy the present invention in the second resin likeThird Example, or even when either MFR or extension viscosity satisfied,the neck-in amount could be decreased but the decreasing effect of theneck-in amount was smaller than in First Example and Fourth Examplewhich satisfy both of them.

[0070] Even if the line speed was so great as 420 (m/min), the firstresin and the second resin could be prevented from film separation andthe suppressive effect against the neck-in could be maintained byarranging the second resin so as to be enveloped in the first resin whenthe first resin forming the center in width direction of the resin filmand the second resin forming both ends in width direction of the resinfilm joined together like Fourth Example. In contrast, when the firstand second resins were joined together so as to adjoin each other likeThird Comparative Example, the film separation occurred and measuringthe neck-in amount was impossible.

[0071] No estimation of film shake was described in FIG. 5, but the filmshake was small with smaller neck-in amount. From this, it followed thatsuppressing the neck-in enabled the film shake to be suppressed.

[0072] When the first and second resins were joined together so as toadjoin each other as shown in FIG. 3(a), the setting temperature of bothends in width direction of the extruder die (corresponding to both endsin width direction of the resin film) was lowered by 40° C. from that inthe test of FIG. 5 and the other conditions were made identical withthose of First Example for the execution with the result that a similarneck-in effect was obtained and also no film separation occurred.Namely, by lowering the resin film temperature at both ends and raisingthe viscosity already at the time point when the resin film was extrudedfrom the extruder die, the film separation could be prevented even whenthe first and second resins were joined together so as to adjoin eachother as shown in FIG. 3(a).

[0073] Next, specific examples of laminate production methods andapparatuses according to the present invention will be describedreferring to FIG. 6. In the following examples and comparative examples,25 μm thick polyethylene was laminated on the surface of a 175 μm thickand 300 mm wide belt-shaped support (original paper). As line speeds,tests were made at a high speed of 300 m/min and a still higher speed of400 m/min in two ways.

[0074] Fifth Example was made by blowing the CO₂ gas from a gas jetnozzle at a line speed of 300 m/min toward a cooling roller direction(in FIG. 6, simply described as “roller surface”) and by the windvelocity of CO₂ gas to 3 m/sec (wind amount: 36 lit./min), the distancefrom the nip point to 45 degrees and the distance from the coolingroller to 20 mm so as to satisfy all the conditions of the presentinvention.

[0075] Sixth Example was the same as Fifth Example except by setting theline speed to 400 m/min.

[0076] Fourth Comparative Example was a case of setting the line speedto 300 m/min without a gas jet nozzle provided.

[0077] Fifth Comparative Example was made by blowing the gas from a gasjet nozzle to the nip point at a line speed of 300 m/min as described inJapanese Patent Application Publication No. 63-246227 and the otherconditions than this were set as with Fifth Example so that only theblowing direction of a gas did not satisfy the present invention.

[0078] Sixth Comparative Example was made like Fifth Example except bysetting the distance from a cooling roller to 60 mm, so that only thedistance from the cooling roller did not satisfy the present invention.

[0079] Seventh Comparative Example was made like Fifth Example except bysetting the distance from a nip point to 100 degrees, so that only thedistance from the nip point did not satisfy the present invention.

[0080] Eighth Comparative Example was made like Fifth Example except bysetting the wind speed of CO₂ gas to 0.5 n/sec, so that only thedistance from the nip point did not satisfy the present invention.

[0081] Ninth Comparative Example was made like Fifth Comparative Exampleexcept by setting the line speed to 400 m/min.

[0082] Tenth Comparative Example was made like Ninth Comparative Exampleexcept by installing a windshield plate made of urethane rubber at theupstream position of a gas jet nozzle in the flow direction of theaccompanying air.

[0083] The laminates produced under conditions of the above Examples andComparative Examples were estimated by measuring the number of cratersper 1 cm² of a resin film. The estimated results are shown in FIG. 6 as“Crater Result”.

[0084] In contrast to Fourth Comparative Example in which the number ofcraters was as extremely great as 350 owing to the provision of no gasjet nozzle, as understood from FIG. 6, the number of craters wasdecreased to 100 for Fifth Comparative Example in which a gas was blowntoward the nip point. The number of craters for Fifth Example in which agas was blown toward the surface of a cooling roller was noticeablydecreased to 40. Namely, though even the gas blowing toward the nip waseffective in the suppression of craters, the effect could be still moreimproved by the gas blowing toward the surface of the cooling roller.This signified that a curtain of gas was formed by blowing a gas towardthe surface of the cooling roller and the shut off of the accompanyingair brought with the rotation of the cooling roller thereby wasnoticeably effective in the suppression of the occurrence of craters.

[0085] As understood from the comparison between the number of cratersequal to 40 for Fifth Example and the number of craters equal to 200 forSixth Comparative Example in which only the distance from a coolingroller did not satisfy the present invention, the suppressive effectbecame small unless the gas blowing position was brought close to thecooling roller surface and specifically the gas blowing position waspreferably 50 mm or smaller from the cooling roller surface.

[0086] As understood from the comparison between the number of cratersequal to 40 for Fifth Example and the number of craters equal to 210 forSeventh Comparative Example in which only the distance from a nip pointdid not satisfy the present invention, the suppressive effect becamesmall unless the distance from the nip point was taken short andspecifically the distance from the nip point was preferably 90 degreesor smaller.

[0087] As understood from the comparison between the number of cratersequal to 40 for Fifth Example and the number of craters equal to 190 forEighth Comparative Example in which only the gas wind velocity did notsatisfy the present invention, the suppressive effect became smallunless the gas wind velocity was taken great and specifically the gaswind velocity was preferably 1 m/sec or greater. In this case, in orderto decrease the number of craters so as to become equal to that of FifthExample under the gas wind velocity condition of Eighth ComparativeExample, the thickness of polyethylene to be laminated had to increaseto 35 Ξm.

[0088] From comparison between Fifth Comparative Example and NinthComparative Example, it followed that the number of craters drasticallyincreased from 100 to 250 according as the line speed rose from 300m/min to 400 m/min under other similar conditions, but also in thiscase, as understood from Sixth Example, the number of craters could bedecreased to 50 by directing the gas blow toward the cooling rollersurface to form a gas curtain.

[0089] From comparison between Ninth Comparative Example and TenthComparative Example, it followed that the number of craters could bedecreased from 250 to 115 by the provision of a windshield plate, buteven in this case could be decreased to 40, equal to the number ofcraters at Sixth Example. In case of a windshield plate installed,sticking of a different matter between the windshield plate and thecooling roller led to the occurrence of fine stripes on the coolingroller and in an extreme case, the surface treatment of the coolingroller had to be done over again.

[0090] With a resin film forming method according to the presentinvention, as described heretofore, the neck-in or the resultantthickening of both ends in a resin film can be suppressed and the filmshake of a change in width of a resin film can be also suppressed evenif the production conditions such as resin condition and operatingcondition change and further the film separation can be prevented evenif both ends and the center of a resin film differ in physical property.

[0091] Thereby, a problem that the film thickness in both ends of aresin film increases in accompaniment with the neck-in and a problem dueto the film separation can be solved and further the material loss canbe reduced.

[0092] Since the speedup of line can be made possible according to thepresent invention, the production efficiency can be improved to a greatextent.

[0093] With a laminate production method and apparatus according to thepresent invention, the occurrence of craters can be inhibited and alaminate excellent in surface appearance can be produced. In particular,even in such a high speed region that the line speed exceeds 300 m/min,the occurrence of craters can be noticeably inhibited, so that theproductivity can be improved. Furthermore, since the number of craterscan be noticeably decreased, the film thickness of a resin film can bealso reduced, thereby enabling the expense of raw materials to be saved.

[0094] It should be understood, however, that there is no intention tolimit the invention to the specific forms disclosed, but on thecontrary, the invention is to cover all modifications, alternateconstructions and equivalents falling within the spirit and scope of theinvention as expressed in the appended claims.

What is claimed is:
 1. A resin film forming method for extruding fusedresin from an extruder die to form a resin film, wherein a resin formingboth ends in width direction of the resin film has an extensionviscosity higher than that of a resin forming a center in widthdirection of the resin film.
 2. The resin film forming method accordingto claim 1, wherein the resin forming both ends of the resin film joinsthe resin forming the center of the resin film so as to be enveloped bythe later resin and is extruded from the extruder die.
 3. A resin filmforming method for extruding fused resin from an extruder die to form aresin film, wherein a resin forming both ends in width direction of theresin film has an MFR smaller than that of a resin forming a center inwidth direction of the resin film.
 4. The resin film forming methodaccording to claim 3, wherein the resin forming both ends of the resinfilm joins the resin forming the center of the resin film so as to beenveloped by the later resin and is extruded from the extruder die.
 5. Aresin film forming method for extruding fused resin from an extruder dieto form a resin film, wherein a resin forming both ends in widthdirection of the resin film has a higher extension viscosity and smallerMFR than those of a resin forming a center in width of the resin film.6. The resin film forming method according to claim 5, wherein the resinforming both ends of the resin film joins the resin forming the centerof the resin film so as to be enveloped by the later resin and isextruded from the extruder die.
 7. A laminate production method forproducing a laminate by nipping a running support and a resin film ofthermoplastic resin by means of a nip roller and a cooling roller whilecoating the surface of the support with the resin film, wherein theaccompanying air brought with rotation of the cooling roller to a nippoint for the support and the resin film is shut off by blowing a gaspermeable through the resin film toward the surface of the coolingroller.
 8. A laminate production apparatus for producing a laminate bynipping a running support and a resin film of thermoplastic resin bymeans of a nip roller and a cooling roller while coating the surface ofthe support with the resin film, wherein a gas jet nozzle for jetting agas permeable through the resin film toward the surface of the coolingroller is provided near a nip point for the support and the resin film.9. The laminate production apparatus according to claim 8, wherein aflow velocity of the gas blown from the gas jet nozzle is 1 n/sec orhigher.
 10. The laminate production apparatus according to claim 8,wherein the gas jet nozzle is disposed at a position such that thedistance from a tip of the gas jet nozzle to the surface of the coolingroller is 50 mm or shorter when blowing the gas vertically to thesurface of the cooling roller.
 11. The laminate production apparatusaccording to claim 10, wherein a flow velocity of the gas blown from thegas jet nozzle is 1 m/sec or higher.
 12. The laminate productionapparatus according to claim 8, wherein the gas jet nozzle is disposedat a position corresponding to a central angle for the cooling roller of90 degrees or smaller, the central angle representing an arc distance onthe cooling roller from a blown point on the surface of the coolingroller for gas blow to the nip point.
 13. The laminate productionapparatus according to claim 12, wherein a flow velocity of the gasblown from the gas jet nozzle is 1 m/sec or higher.
 14. The laminateproduction apparatus according to claim 12, wherein the gas jet nozzleis disposed at a position such that the distance from a tip of the gasjet nozzle to the surface of the cooling roller is 50 mm or shorter whenblowing the gas vertically to the surface of the cooling roller.
 15. Thelaminate production apparatus according to claim 14, wherein a flowvelocity of the gas blown from the gas jet nozzle is 1 m/sec or higher.